Spark plug



0. C. ROHDE Nov. 12, 1935.

SPARK PLUG Filed Jan. 25, 1934 Ticll Patented Nov. 12, 1935 UNITED STATES PATENT OFFICE SPARK PLUG poration of Delaware Application January 25, 1934, Serial No. 708,231

3 Claims. (Cl. 123-169) This invention relates to a spark plug and more particularly to a spark plug in which the insulator core is fixed in position within the shell by-metal cast betweenthe core and shell. De-.

' tails of the invention will appear as the description proceeds.

In the accompanying drawing forming a part of this specification, Fig. l is an elevation of a spark plug in accordance with the invention; Fig. 10 2 is a longitudinal section of the spark plug; and

Fig. 3 is a similar section of a portion of a somewhat modified form of the plug.

In the construction illustrated there is the usual metallic shell l having a screw threaded por- 15 tion I I adapted to be screwed into the cylinder in an internal combustion motor or the like. The lower end 01' the shell is shown with two upwardly facing shoulders I 2 and IS. The insulating core I4 is shown with corresponding down- 20 wardly facing shoulders I5 and IS. A sealing washer I! is shown between shoulders l6 and I3. The upper portion of the shell is provided with a cylindrical bore l8 in which there is a locking groove l9. Between the shell and the core with- 25 in this bore there is provided sealing material. In the form shown the lower part of the pocket between the core and'the shell is filled with powdered material 20 which may be powdered soapstone or the like. Above this powdered material, so which is compacted'in place, there is a ring or sleeve 2| of metal cast in place,preferably aluminum. In the upper end of the pocket, as a finish above the cast aluminum, there is a ring 22 of copper or the like. Preferably ring 2| is com- 35 posed of aluminum cast in place by means of electrically melting powdered aluminum in the upper end of the pocket and compressing it by means of ring 22. This results in a very accurately fitting aluminum ring which enters into 40 locking groove l9 and exactly fits the interior wall of the shell and the exterior of the core. At

the same time it is somewhat more porous than ordinary cast aluminum, because of the method by which it is produced, since the air in the pow- 45 dered aluminum is trapped to a certain extent.

With the core assembled within the shell, as described, the central electrode 23 is in suitable sparking relation with electrode 24 attached to shell ID in the usual manner.

50 Figure 3 shows a similar construction, the shell l0 being the same as in Fig. 2, but the core being divided into two parts, an upper part Me and a lower part Mb having between them a plane of cleavage 25. In this case the lower portion Hi,

55 is substantially the same in shape as the lower end of core I! shown in Fig. 2, and the upper end la, is similar to the upper end of core l4 except that there is a shoulder 26 provided a short distance above the plane of cleavage 25. It will be seen that the insulating powder 20. 6 which may be soapstone or the like, surrounds the plane of cleavage 25 and forms insulation between the shell and this plane of cleavage. Above the soapstone powder there is a ring or sleeve of cast aluminum 2|e similar to the sleeve 2| de- 10 scribed above, and also there is a finishing ring of copper 22a similar to ring 22. The rings 2|n and 229. are shown somewhat wider than rings 2| and 22 so as to provide for the extra. shoulder 26.

It willbe seen that in this construction the two parts 01' the core are held together by the means which holds the core in the shell, and that the line of cleavage between the two parts of the core is surrounded by powered soapstone 20,1,

which forms an eflective insulator and prevents any leakage which otherwise might take place through the line of cleavage from central electrode 23 to shell Hi.

It will be readily seen that, in this form, equivalent insulating material might be substituted for 25 the powderedsoapstone mentioned, provided it would withstand the heat towhich it is subjected when aluminum ring 20a. is melted in contact therewith. In the form shown in Fig. 2 it is not essential that material constituting ring 20 should be of soapstone or even that it should be insulated material, but it has been found that the pow dered soapstone is quite desirable as it forms a sufficiently tight seal between the core and shell, so, as to close the bottom of the pocket therebetween, and at the same time yields slightly to pressure exerted thereon as a result of differences in expansion of the core and shell. As indicated above, with a construction such as shown in Fig.

3, it is highly desirable to have this ring of nonconducting material so that it provides security against leakage through the plane of cleavage between the two portions of the core. In both. forms the ring 20 or 201,, respectively, seals the bottom of the pocket into which the powdered aluminum is placed and prevents the molten aluminum from running down between the core and the shell, which it might do to some extent if the space therebetween was not sealed. In the form shown in Fig. 2 this sealing of the bottom of the pocket might be obtained by other materials, even conducting materials, if they are otherwise of suitable nature.

The ring 2| produced from powdered aluminum molten in place is particularly desirable for sealing the core within the shell since it accomplishes this function securely and at the same time is soft and yielding enough to avoid breaking the core. Also the heat necessary for melting such powder is not as high as it would be with steel or iron powder, for example, which might result in excessive strains on the core. It will be readily understood that other metallic powder or mixtures of powder or granular material having characteristics similar to those of the powdered aluminum, both as to suitability for melting in place and avoiding excessive heat or excessive strains upon the core, might be substituted for the aluminum powder. It will also be understood that the exact shape of the shell or core is not vital to the broad principle of this invention and the example shown is by way of illustration only.

In some instances granules of non-conducting material might be included with the aluminum or other conducting material, providing the conducting material is sufliciently continuous to carry a melting current, and is of a nature which will not injuriously affect the locking ring after is has been cast.

A core of porcelain or similar ceramic material may be secured in this manner within shell and form a permanently gas tight plug without excessive breakage of the cores. In the form shown in Fig. 3 thelower portion I); o! the plug my be of more expensive material than the upper end of the core, if this is desired to make the lower end of the core sumcientiy resistant to the condition it encounters in the firing chamber. 5

What is claimed is:--

1. A spark plug comprising a shell and insulating core having a uniting pocket therebetween and porous metal fitted in said pocket by electricaliy melting and compressing therein granu- 1o lar material including the metal.

2. A spark plug comprising a shell and core having a uniting pocket therebetween and porous aluminum fitted in said pocket by electrically melting therein granular aluminum. 15

3. A spark plug comprising a metal shell, a central electrode, a two piece ceramic core around said electrode and having a transverse plane of cleavage between the two pieces, a shoulder on the shell supporting one 0! said pieces, a shoulder go on the other piece facing in the same general direction as the shoulder on the shell, granular insulating material compacted around said plane of cleavage and inside of the shell. and metal cast between the shell and core and against said granu ular material and holding said granular material and core pieces in place within the shell.

OTIO C. ROH'DE. 

